1. Technical Field
The present invention relates to an ink composition containing a fluorescent dye and an ink jet recording method using the same.
2. Related Art
In postage meters for printing postage or postal indicia, red fluorescent ink has been used. In particular, in North America, red fluorescent ink that can be read by automatic readers used by the United States Postal Service is designated as ink to be used for postal indicia.
Automatic readers read bar codes and also detect the front and back of pieces of mail at the same time. Consequently, the red fluorescent ink is required to have not only a high optical density in order to improve bar-code reading accuracy, but also a high fluorescence intensity in order to reduce errors in detecting the front and back of pieces of mail to be detected.
JP-A-9-291246 (Patent Document 1) discloses, as a fluorescent ink for metered mail, a red fluorescent ink to which glycol ether has been added as a cosolvent penetrant and which has excellent waterfastness.
Furthermore, JP-A-2006-131667 (Patent Document 2) discloses an aqueous fluorescent ink having good fluorescent color developability in which a water-soluble fluorescent colorant including C.I. Acid Reds 52 and 92 as fluorescent dyes and a pigment dispersion solution including C.I. Pigment Red 122, as a pigment, and the like are used in combination.
However, fluorescent dyes have poor lightfastness, and when another dye or the like is mixed therewith in order to improve lightfastness, the fluorescence intensity may be sharply decreased because of interaction between the fluorescent dyes and the other dye in some cases.
Furthermore, by combining C.I. Direct Yellow 87 with a red fluorescent ink composition including C.I. Acid reds 52 and 92, a red fluorescent ink composition excellent in terms of fluorescence intensity and color developability (optical density) has been provided (refer to JPA-2009-256544: Patent Document 3). However, an ink composition having good lightfastness in which fluorescence intensity and color developability (optical density) are not impaired has been strongly desired.